Hollow Valve For An Engine

ABSTRACT

The embodiments of the present invention comprise a coolant-free hollow valve with a cavity and a vacuum being enclosed in the cavity. The valve is used for an engine and one example of an engine is an internal combustion engine. The valve comprises a coolant-free hollow vacuum cavity to reduce the heat conduction such that the combustion heat is used to perform useful work to improve the efficiency of the engine. One embodiment of the present invention is a coolant-free valve with a hollow vacuum cavity and a thermal barrier coating being deposited onto part of the external surface of the valve that comes into contact with the combustion chamber of the engine.

FIELD OF THE INVENTION

This application relates generally to valves used in internal combustionengines. More specifically, this application describes a coolant-freehollow valve with a vacuum cavity.

BACKGROUND OF THE INVENTION

Valves are essential components of internal combustion engines toregulate the intake of fuel and air as well as the exhaust of thecombustion products. An alternative name for the valves for internalcombustion engines is poppet valves. As shown in FIG. 1A, a typicalvalve consists of a long valve stem 200 and a broad valve head 100.Combustion inside an engine produces heat and the hot gas reaches a hightemperature to produce useful work such as propelling an automobile orrotating a generator to produce electricity. A surface 110 of the valvecomes into contact with the combustion chamber and is exposed to hightemperatures. In addition to the solid (cavity-free) valve schematicallyillustrated in FIG. 1A, there are hollow valves with cavities that arefilled with a coolant having a low-melting metal such as sodium toconduct the heat away from the head of the valves in order to preventthe valve head 100 from heat damage and to prolong the lifetime of thevalve by reducing the temperature of the valve head 100. U.S. Pat. Nos.1,670,965 and 9,611,953 and the patents cited within the '953 patentdisclose prior art hollow valves.

These various hollow valves described above and schematicallyillustrated in FIG. 1B all purposely use a cavity filled with a coolant1000, a low-melting point metal, and most predominantly sodium, toconduct heat away from the valve head 100 to prolong the lifetime of thevalve. Because part of the heat inside the engine is extracted away bythe valves instead of being used to do useful work, these valves havethe negative effect of reducing the efficiency of the engine.

Solid valves without a coolant filled cavity are also widely used inengines. Even for these solid valves, the heat conduction from themamounts to a significant part of the heat loss of the engine and thusleads to reduced efficiency. Some of the solid valves also have aninternal cavity 2000 that is used primarily to reduce the weight of thevalve, as schematically shown in FIG. 1C. An example of such a valve isdisclosed in U.S. Pat. No. 5,413,073. The internal cavity in such avalve is not evacuated.

U.S. Pat. No. 9,790,822 discloses a two-cavity poppet valve, asschematically shown in FIG. 1D. A small cavity within the valve stem 200is partially filled with a coolant (sodium) 1000 with the remainingspace in the cavity being filled with an inert gas 3000. A large cavity4000 inside the valve head 100 is filled with insulation with examplessuch as an inert gas, partial vacuum, vacuum, and heat-resistant metalor carbon as a filter. Even though the '822 patent recognized thebenefits of insulation, the solutions are very complex and requireseveral manufacturing steps to make the two-cavity valve, which may leadto prohibitive cost. The valve in FIG. 1D also requires a cap 120 madeup of a low conductivity heat resistant material to be welded onto anopening (necessary for manufacturing access) at location 130 at thecombustion-facing surface 110 of the valve head 100. Because the surface110 of the valve head 100 comes into contact with the combustion chamberof the engine, it is exposed to the harsh, high-temperature environment;welding of two different materials (one for the cap 120 and one for thevalve head 100) at this surface may lead to accelerated degradation dueto the mismatch of the coefficients of thermal expansion of the twomaterials and reduction of properties at the weld joint.

SUMMARY OF THE INVENTION

Accordingly, the above-identified shortcomings of prior art valves areovercome by embodiments of the present invention. Embodiments of thisinvention comprise of a coolant-free hollow valve in an engine wherein avacuum is enclosed in a cavity, thereby providing better insulatingproperty to the valve. By removing the coolant altogether and theassociated manufacturing steps, the present invention will lead tobetter insulation and more manufacturing flexibility and lower cost forthe valve. The removal of the coolant cavity also allows the entirecombustion-facing surface 110 of the valve head 100 to be made of oneheat-resistant material without any welding on that surface, thusshifting the welding-induced vulnerability to less critical and easierto manufacture locations.

The vacuum is broadly defined in the present invention as from reducedor partial vacuum such as one hundredth of an atmospheric pressure tohigh vacuum conditions. The vacuum definition in this inventioncomprises vacuum achieved through simple mechanical pumping to moreadvanced vacuum technologies that are all known in the art. The presentinvention discloses a coolant-free hollow valve in an engine, the valveincluding a cavity in the valve and a vacuum being enclosed in thecavity.

In one embodiment of the present invention, a thermal barrier coating6000 is deposited onto the combustion-facing surface 110 of the valvehead 100 to further improve the thermal insulation property of thevalve.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and embodiments of the present invention will become moreapparent from the following descriptions of the accompanying drawings.

FIG. 1A depicts a central longitudinal cross section of a prior artround, solid valve.

FIG. 1B depicts a central longitudinal cross section of another priorart round valve with a cavity partially filled with a coolant (sodium).

FIG. 1C depicts a central longitudinal cross section of yet anotherprior art valve with a hollow, unevacuated cavity.

FIG. 1D depicts a central longitudinal cross section of yet anotherprior art valve with a cavity partially filled with a coolant with theremaining space being filled with an inert gas, and a second cavityfilled with insulation.

FIG. 2A depicts one embodiment of the present invention in a centrallongitudinal cross sectional view showing a coolant-free valve with acavity in a state of vacuum.

FIG. 2B depicts another embodiment of the present invention in a centrallongitudinal cross sectional view showing a valve with a cavity in astate of vacuum.

FIG. 2C depicts yet another embodiment of the present invention in acentral longitudinal cross sectional view showing a cavity in a state ofvacuum, and a thermal barrier coating deposited onto a combustion-facingsurface of the valve head.

These drawings are intended to facilitate the description of the presentinvention. They are by no means limiting the various embodiments andvariants of the present invention. Further features, aspects, andadvantages of the present invention will be more readily apparent tothose skilled in the art during the course of the following detaileddescription.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of promoting an understanding of the invention, theterminology used herein is for the purpose of description, notlimitation. Specific geometries, methods and processes disclosed hereinare meant to be used as examples. Various variants or embodiments shouldbe considered as part of this invention.

Prior art valves conduct heat through the metal or intentionallyaccelerate the heat conduction using a low-melting point metal coolant,predominantly sodium, to conduct heat away from the valve duringoperation. Even the most recent two-cavity valve disclosed in the '822patent still uses sodium coolant to conduct heat away even though the'822 patent recognizes the need to have a separate insulation cavity.Such prior art valves conduct significant amount of heat away from theengine and thus lead to reduced efficiency. The present inventionremoves the coolant altogether and uses a vacuum cavity in the valve toachieve better insulation (instead of better heat conduction) so thatmore heat can be kept inside the engine to perform useful work such aspropelling a vehicle or driving a generator to produce electricity.

Three example embodiments of this invention are schematically shown inFIG. 2A, FIG. 2B, and FIG. 2C. These drawings are for illustrationpurposes and various variants and modifications should be consideredpart of this invention to those who are skilled in the art.

FIG. 2A is one embodiment of the current invention where a coolant-freehollow vacuum cavity 5000 extends to near a stem tip 400 for betterinsulation as well as reduction of the weight of the valve. Variousmanufacturing methods known in the art can be employed to make thevalve. One embodiment of the manufacturing methods is to use additivemanufacturing (AM) to make both a valve head 100 and majority of a stem200, from the bottom up to location 1 in FIG. 2A. AM is also termed 3Dprinting and other alternative names. AM apparatus melts powders layerby layer or wires to build structures and components and it is amanufacturing method that is known in the art. The stem tip 400 can thenbe attached at location 1. An example of the joining process is weldingand another example is brazing, both are known in the art. Both weldingand brazing can be performed inside a vacuum chamber such that duringand after joining, the coolant-free hollow cavity 5000 inside the valveis in a state of vacuum. An alternative embodiment of the manufacturingmethod is to perform the joining in air or under a protective gas suchas argon environment, but leave a small evacuation hole 500 in the stemtip 400 to allow evacuation after the joining and then seal off toretain the vacuum inside. Such evacuation scheme is known in the art.The location of the joining can be selected, for instance from location1 to location 2 to location 3, based on the relative ease and cost ofmanufacturing. These locations can vary depending on the valve designand manufacturing process and are put on FIG. 2A for illustrationpurpose only.

One embodiment of the invention is to use electron beam (EB) weldingthat is known in the art. The EB welding is usually performed inside avacuum, thus there is no need for an additional evacuation step. Anotherembodiment of this invention is to use friction welding which is againknown in the art. During the friction welding process, one piece isrubbed against another piece at high speed until they are joinedtogether. Most friction welding is performed in air; and in this case,an extra evacuation step is needed similar to the process explainedheretofore. Alternatively, the friction welding can be performed insidea vacuum chamber, and in this case, the welded cavity will beautomatically in a state of vacuum. The friction welding motion can berotational instead of linear for the joint 220 (FIG. 2B).

One further embodiment of this invention is shown schematically in FIG.2B. Part of the stem 200 (above point 4) remains solid without a hollowcavity, which facilitates the friction welding process. The cost of thesolid stem can be lower than that of another stem with a cavity.Location 4 can vary depending on the requirement of the engine withconsideration of the cost of manufacturing the entire valve.

Yet another embodiment of the present invention entails a thermalbarrier coating 6000 being deposited onto the combustion-facing surface110 of the valve head 100, as schematically illustrated in FIG. 2C.Thermal barrier coatings are known in the art to those skillful inengine technologies.

The valve disclosed in the current invention is made up of heatresistant materials such as high-temperature alloys that are known inthe art. In one embodiment of this invention, the valve head 100 and thevalve stem 200 are made up of different heat-resistant materials.Because the stem 200 is exposed to much lower temperatures, it can bemade up of a low cost material.

In addition to AM, other manufacturing processes can be used to make thevalve of the present invention and its various components. Technologiesknown in the art to make sodium-filled hollow valves can be used to makethe valve of the present invention. Instead of filling the cavity withsodium, a vacuum can be created in a cavity 5000.

One embodiment of the present invention employs casting to make thevalve head 100 and the stem 200. Casting is a cost-effective technologywidely used to make components, especially metal components.

Another embodiment of the present invention employs forging to make thevalve head 100 and the stem 200. Forging is already widely used to makevalves.

When AM is used to make the valve components such as the valve head 100,various structural features can be introduced into the valve head cavityto improve its mechanical performance.

Various embodiments of the present invention have been described infulfillment of the various needs that the invention meets. It should berecognized that these embodiments are merely illustrative of theprinciples of various embodiments of the present invention. Numerousmodifications and adaptations thereof will be apparent to those skilledin the art without departing from the spirit and scope of the presentinvention. It is intended that the present invention cover all suitablemodifications and variations as come within the scope of the appendedclaims and their equivalents.

What is claimed is:
 1. A coolant-free hollow valve for use in an enginehaving a combustion chamber, the valve comprising: a valve stem; a valvehead having a weld-free, combustion-facing surface that is adapted tocome in contact with the combustion chamber of the engine; a cavity inthe valve head; and a vacuum being enclosed in the cavity.
 2. Thecoolant-free hollow valve of claim 1, wherein the cavity is formed inthe valve head and in at least part of the valve stem; and the vacuumbeing enclosed in the cavity.
 3. The coolant-free hollow valve of claim1, wherein the cavity is formed in the valve head and the valve stem;and the vacuum being enclosed in the cavity.
 4. A coolant-free hollowvalve for use in an engine having a combustion chamber, the valvecomprising: a valve stem; a valve head having a weld-free,combustion-facing surface that is adapted to come in contact with thecombustion chamber of the engine; a cavity in the valve head; and avacuum being enclosed in the cavity; and a thermal barrier coating beingdeposited on at least part of the combustion-facing surface of the valvehead.
 5. The hollow valve of claim 4 wherein the engine is an internalcombustion engine.
 6. The coolant-free hollow valve of claim 4, whereinthe cavity is formed in the valve head and in at least part of the valvestem and the vacuum being enclosed in the cavity.
 7. The coolant-freehollow valve of claim 4, wherein the cavity is formed in the valve headand the valve stem and the vacuum being enclosed in the cavity.
 8. Thecoolant-free hollow valve of claim 1, wherein the valve head and thecombustion-facing surface are made of the same material.
 9. Thecoolant-free hollow valve of claim 4, wherein the valve head and thecombustion-facing surface are made of the same material.
 10. The hollowvalve of claim 1 wherein the engine is an internal combustion engine.